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Month: March 2015

This is a simple mechanism, using DNS to certify that email from your domain comes from authorized servers. This is accomplished by adding a DNS record to identify the servers from which you send legitimate email. Emails sent from other servers MAY then be assumed as forged (SPAM) and blocked by the receiving email server.

NOTE: This can be easily spoofed, as such it should be a portion of your email security strategy, look into DKIM and DMARC too!

One thing that I initially did not understand… if you are supporting IPv6 and IPv4, you should merge your records onto a single DNS TXT entry:

Website network performance is usually a very complicated process. Over the years, I’ve outlined many development techniques that can be used toward this goal. I’d heard about mod_pagespeed for some time, but never had the opportunity to experiment with it until recently. My first impression is that it is a VERY EASY means to gain performance improvements without reworking your existing website to implement techniques for establishing far-future expires, cache-busting, minification and static file merging.

Out of the box, most common techniques are automatically applied to your assets and a local server cache is created to utilize them.

Default installation is trivial:

Download the latest version for your server architecture:
wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-stable_current_amd64.deb

OR
wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-stable_current_i386.deb

sudo dpkg -i mod-pagespeed-*.deb

sudo apt-get -f install (if required)

sudo service apache2 restart

NOTE: Using tools like Firebug will enable you to see an HTTP Header indicating the version being used for your requests.

If you need to modify configuration from the default:
sudo vi /etc/apache2/mods-available/pagespeed.conf

For VirtualDomains, you can selectively enable and disable PageSpeed and many of it’s settings in your appropriate configuration files with:
<IfModule pagespeed_module>
ModPagespeed on
</IfModule>

NOTE: Appending ?ModPagespeed=off to your URL will disable functions for that request.

This HTML4 attribute was intended to defer/delay execution of specific javascript code until after the page is rendered. In theory, this makes the website “appear” faster as the functions relevant to the User-Interface can be executed before other “background” processes that would otherwise block the screen from displaying.

<script defer="defer" src="example.js"></script>

NOTE: Do not use defer for external scripts that might depend on each other if you need to support MSIE9 and earlier.